Corrosion Science and Technology

The Corrosion Science Society of Korea (한국부식방식학회)
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Effects of Cooling Rates of Coating Layer on Microstructures and Corrosion Behaviors of Zn-Al-Mg Alloy Coated Steel Sheets

Zn-Al-Mg 합금도금강판의 도금 층 냉각속도 제어에 따른 미세조직 및 부식거동 분석

  • Lee, Jae-Won (Pohang Institute of Metal Industry Advancement (POMIA)) ;
  • Kim, Sung Jin (Department of Advanced Materials Engineering, Sunchon National University)
  • 이재원 (포항금속소재산업진흥원소재솔루션연구실) ;
  • 김성진 (순천대학교신소재공학과)
  • Received : 2022.06.11
  • Accepted : 2022.06.21
  • Published : 2022.06.30
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Abstract

To understand effects of cooling rates of coating layer on microstructures and corrosion behaviors of hot-dip alloy coated steel sheets (Zn-5%Al-2%Mg) in a neutral aqueous condition with chloride ion, a range of experimental and analytical methods were used in this study. Results showed that a faster cooling rate during solidification decreased the fraction of primary Zn, and increased the fraction of Zn-Al phase. In addition, interlamellar spacing became refined under a faster cooling rate. These modifications of the coating structure had higher open circuit potentials (OCP) with smaller anodic and cathodic current densities in the electrochemical potentiodynamic polarization. Surface analyses after a salt spray test showed that the increase in the Zn-Al phase in the coating formed under a faster cooling rate might have contributed to the formation of simonkolleite (Zn5(OH)8Cl2·H2O) and hydrotalcite (ZnAl2(OH)6Cl2·H2O) with a protective nature on the corroded outer surface, thus delaying the formation of red rust.

Keywords

Acknowledgement

순천대학교 교연비 사업에 의하여 연구되었음.

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